1. Field of the Invention
The present invention relates to a drive circuit for driving a display element such as an organic light-emitting diode (hereinafter denoted by OLED) element and the like, and an image display apparatus using the drive circuit.
2. Description of the Related Art
An active matrix (hereinafter denoted by AM) type OLED display has been studied recently as a light emission display device having pixels arranged in a matrix shape, each pixel being constituted of an OLED element and a drive circuit.
FIG. 26 shows an outline structure of a pixel circuit constituted of an OLED element and a drive circuit.
FIG. 27 shows an AM type organic display having the pixel circuits arranged in a matrix shape.
FIG. 28 shows an example of the pixel circuit.
SW1 and SW2 are turned on, and current is supplied from an external (L3) to a TFT (Tr1) in the pixel circuit whose gate and drain are shorted.
A gate voltage value Vg1 of TFT can therefore be set to a voltage at which the external current flows as a drain current.
Current flowing a light emission element can thus be set.
Thereafter, in the state that the gate voltage value Vg1 is retained, SW1 and SW2 are turned off and SW3 is turned on to switch a current path to the OLED element (LED1) side.
Since a voltage between the gate and source of TFT is the same voltage at which the current from the external L3 flows, TFT (Tr1) functions as a current source for supplying a constant current having the same amplitude as that of the external current. Namely, current having the same amplitude as that of the current from the external (L3) flows through the OLED element.
A display element operating by the current drive described above is described in International Publication No. WO99/065011.